1. Technical Field
The present invention relates to a liquid crystal display device for driving liquid crystal by a horizontal electric field and an electronic apparatus equipped with the same. In particular, the present invention relates to a liquid crystal display device of a transflective type in which a transmissive area and a reflective area are provided in each of a plurality of pixels and a retardation layer is formed in the reflective area.
2. Related Art
In order to provide a wide viewing area in a liquid crystal display device, a liquid crystal display device of a type in which liquid crystal is driven by a horizontal electric field by so called a fringe field switching (hereinafter, referred to as FFS) system, an in plane switching (hereinafter, referred to as IPS) system, and the like have been put into practical use. Further, in such a type of liquid crystal display device, a transflective type liquid crystal display device in which a transmissive area and a reflective area are provided in each of a plurality of pixels have been proposed.
Further, under the assumption that to minimize the influence of viewing angle dependence property of the retardation film, it has been proposed to employ the structures described below in order to solve a difference of the retardation value caused by a difference of the length of the pathway through which light is transmitted in a transmissive mode and a reflective mode (see JP-A-2005-338256 (hereinafter, referred to as Patent Document 1)).
(a) provide a retardation layer in a reflective area;
(b) dispose a first polarizer and a second polarizer so that the polarization axes thereof are perpendicular to each other;
(c) the alignment direction of liquid crystal is parallel to the polarization axis of the first polarizer;
(d) the angle made by the slow axis of the retardation layer and the polarization axis of the first polarizer is about 22.5°;
(e) the retardation value of a liquid crystal layer in the reflective area is a quarter wavelength; and
(f) the retardation value of the retardation layer is a half wavelength.
That is, the structures are employed in which the retardation layer is provided only in the reflective area under the condition that the display is not disturbed in the transmissive mode, the polarization axis of the polarizer and the alignment direction of liquid crystal are set so as to be parallel to or perpendicular to each other, and the retardation of the liquid crystal layer in the reflective area is set to a quarter wavelength and the retardation of the retardation layer is set to a half wavelength.
In such conditions, in order to perform black display in the reflective area, if the angle between the polarization axis of the polarizer and the slow axis of the retardation layer is α and the angle between the polarization axis of the polarizer and the alignment direction of liquid crystal (alignment axis of liquid crystal) is β, it is required to basically satisfy the following formula.β=α×2±45°
Further, if consider the above described structure, as β becomes 0° (or 180°), α inevitably becomes 22.5° (or about 67.5°).
However, in the structures (a) to (f) disclosed in Patent Document 1, as is regulated by the structures of (e) and (f), if the retardation value of the liquid crystal layer in the reflective area with respect to the light whose wavelength is 550 nm is set to the quarter wavelength, when Δn of the liquid crystal layer is about 0.12, the thickness of the liquid crystal layer have to be set to an extremely thin thickness of about 1.1 μm. As a result, there is a problem in that it is difficult to provide mass production.